共查询到20条相似文献,搜索用时 211 毫秒
1.
CAO Hui 《声学学报:英文版》1995,(4)
I.IntroductionItisdifficulttoanaIysesoundscattcringfromanedgeofathickpIatetheoretica11y.Inmostprevious.ork['-'],thecdgcdifTractionsofidca1ha1fp1aneswereconsidered,i.e.theplanesarepcrfcct1yhardorpcrfcctlysoftoroncsurfacehardandonesurfacesoftandtheirthicknessisneg1cctcd,thccorrespondingthporicsarcquitecomp1ctc.Inthisstudy,thecdgcscattcringfromthickelasticplatesinwatcrisinvestigated.Theex'perimentalrcsultsarccxamincdphysica1lybythcp1atethcoryandcomparcdquantitative1ywithca1culationsfromanumeric… 相似文献
2.
WU Shuoxian 《声学学报:英文版》1994,(3)
I.IntroductionTherearetwowaysofcvaluatingconcertha1lacoustics.Oneistoevaluatetheacousticalqualityofaconcertha11ateachlistener'spositionrespectively,andtheotheristoevaluatetheacousticalqua1ityofaha1lasawho1e.Bothwaysarebasica1lysimilar.Howcvcr,sincesomcob-icchveparametersmayhavedifTerentvalucsatdifferentpositions,onemustdcfinesuitab1ein-dicestodescribetheseparameters(e.g.meanva1ucsorothers),sothatacomparisonbetweenha1lsbecomcspossib1e,Thispaperdea1swiththelattereva1uationbyusingfuzZysettheory… 相似文献
3.
I.IntroductionTheinvcrseprob1cmofsoundscattcringisinterestingtou1trasonicdiagnosis,identificationofanundcrwatcrtargct,speechsynthesisctc.UsingthismethodDucheneandTabbara[1.21.studiedtheu1trasonicdiagnosisofab1oodvessel.Inthispaperweusedasoft-tubetosimulateabloodvesselanddeaIswiththeu1trasonicdiagnosisofthesofc-tube.Invcrsescatteringprob1emdcterminingatubeparamctcrswasgivcn.Agcomctrica1acousticsmethodwasuscdindescribingthescattcrcdfield.Fivcparametcrsofthctubcwercrcconstructcd.Therelativcdc-… 相似文献
4.
I.IntroductionTheprob1cmofsuppressingstrongpointinterferencesourceisavcryimportantthesisinsonardesign.Fortheana1ogsonar,thesolutionofthisprob1emisquitedifficu1t.Untilthedevelopmentofdigitalsonar,thereissomerescarchreportsaboutsuppressingstrongpointin-terferencesource.Theear1ierworkin1969,dedicatcdbyV.C.Anderson,istheconccptofDICANNE(DigitalInterfcrcnceCance1lingAdaptiveNu1lNetworkEquipment)['l.Thisisadoublecompensatormulti-bcamsystcm.Oneisusedtoformintcrfercncebeamandanothcrisusedtofor… 相似文献
5.
I.IntroductionThedigita1operationins0narsystembringsagreatadvantageinbeamforming.Itispos-sib1etorealizesomcalg0rithmsindigita1technique,whichisusua11yhardtoorimpossib1etoAnp1ementintraditiona1ana1ogues0nar.Asanexamp1e,ageometrygraphofcirclearrayisil-1ustratedinFig,1.Thetotalnumber0farraye1ementisN.Therearetwokindsofbeam.TheA-c1assbeamconsistsof2M-le1ements,thesteeringdirectionisjustlocatedintheposi-honofoneofthearrayelement;TheB-classbeamconsistsof2Me1ementsandthesteeringdirectionisinthem… 相似文献
6.
I.IntroductionApostbeamformernoisecancel1erisasing1e-channeladaptiveprocessorinbeamspace['l.Ithasnotonlysimplerstructure,buta1sobetterpropertiesthane1ementspaceprocessorinimp1ementation.L.C.GodaraandA.Conto1ihavestudiedthesignaltonoiseratioofthebroadbandPIC[1].Theauthorshavesolvedtheprob1emofapplicationconditionsofnarrowbandPIC['],andproposedthatRMGSEFa1gorithmistheoptimuma1gorithminthenarrowbandPICadaptiveprocessing['1.Atpresent,thepfob1emofadaptivecance11ingofbroadbandtowing-shipnoi… 相似文献
7.
I.IntroductionUptonowtheultrasonicpu1seechotechniquehasbeenwide1yusedinthefieldofnon-destructivetesting.Toachievehightargetreso1ution,narrowpu1seshou1dbeadoptcd.Butthiswill1imitthetransmitpowerandthcdetectab1erange,whichisveryboportantcspecia1lyinthemediumwithstrongacousticattenuation.Itmeansthatthetargetresolutionanddetcctablerangehavccontradictorydcmands.Thcrcforethepulsccompressionandcorre1ationtechniqucdeve1opedinradarsystemhavebeenintroducedintotheultrasonicNDTandsomeprogresseshavebeenp… 相似文献
8.
ZHAO Songling 《声学学报:英文版》1994,(3)
I.IntroductionFluteisanancientmusicinstrument.Itsprincipa1structureisasegmentofcircu1arpipewithaseriesofaperturesonthewa11.Amongtheseapertures,oneisca11edblowingapertureandothersarecalledtuningapertures.Duringperformance,thep1ayerb1owsbythecdgeofblowingapertureandcontro1sthetuningapertureswithcertainfingeringtoexcitedifferentpuretones.Forapopularflute,onetcrmina1ofthcfluteisopenandtheothcrisclosedwithapiston.Thetuningaperturesaresett1edneartotheopenterminalandtheblowingapertureneartotheclose… 相似文献
9.
LI Zhichun 《声学学报:英文版》1995,(1)
I.IntroductionItiswe11knownthatultrasonicwavecanbegenerated'bytherma1expansionwhenalaserbeamisincidentonsamples.Accordingto1incarthcory,laserultrasonicsignalcanbcderivedfromtheso1utionofthermoe1asticdifferentialcquationinwho1espacc.Asanimportantparameter,theamp1itudeofsoundwavehasbeenappliedtoquantitutivemeas.rements['-3l.Recentpapersbegintofocusonanotherconsiderablecharactcr-thctempora1profileofultrasonicsignalwhoscfrequencyandphasespectruminvolvemoreinfOrmationofmaterialproperhesl~8l.And,c… 相似文献
10.
I.IntroductionInordcrtocfficlcntlyprcdictandcontro1thenoiseinindustria1enclosurcs,manypeoplehavestudicdmathmodclsforsoundpropagationinindustria1enclosurcs.Butsofar,thereisnosatisfactoryrcsult.Inthepast,a1mostal1studieswcrercstrictedtoidealemptyindustrialcnc1osurcs,andonlyafewofthcm['-']concerncdtheinfluenceofobstac1cswithinthemodel.Thcscmodc1strcattheobstac1eeffcctsbythemethod-ofimagesandcanonIybeusedtoregu-larhexahcdronroomswhcreobstaclcsareassumedtobedistributesuniformIy.Ondet'sartic1el'],… 相似文献
11.
Ruan Shixun 《声学学报:英文版》1994,(2)
1.IntroductionThemaximumoutputofatransformeramplitudeislimitedbythefatigueofthema-tCrialusedlll.Ifthesurfaceshearstressofatorsionaltransformer,T,isuniformalongtheaxis,inotherwords,themaximumpointofsurfaccshearstrcssisincxistent,ti.ea1lowab1coutputpowcrofthetorsionaltransformerwillenormouslyincrease.Insomecasesinwhichveryhigh-intcnsitytorsiona1ultrasonicpowerisrequired,theywil1benecessaries.Forthispurpose,wederivedthenewtypeoftorsionalangletransformer-quartcr-wavelcngthhypcrbolicsccanttaper.T… 相似文献
12.
CHEN Tong 《声学学报:英文版》1995,(2)
I.IntroductionInmanycasesthecontinuityofsoundpropagationwithinatubeisbrokenbyaperturesonthetubewallsuchastoneholesonthemainboreofwoodwindmusicalinstruments,rectangularsound-windowofChineseinstrumentshengetc.Thediscontinuityhaseffectonwavccncoun-tCringit.Keefestudicdasing1etoneholeofwoodwindinstrumentandrepresenteditbyaT-sectionequiva1entcirc.it[11.Inthispaper,theapertureontubewa1lisstudiedfromdifferentpointofview,a1thoughtheGreen'sfunctionmethodisalsousedinthetheoreticalana1ysis.Moresimp1er… 相似文献
13.
I.IntroductionTheacousticbeams'f0cusingandscanninggeneratedbytransducerarraysonso1idsurfacep1ayaveryimportantroleinacousticimagingandultrasonoc1ectronicdevices.InourpreviouSworkt'-'],weinvestigatcdtheproperties0ftheacousticbeams'focusingandscanninga1ongthesymmetricalaxis,acousticfic1ddistributioninthewho1espaceandnearthefocus.Andwealsogaverigoroustheoretica1ana1ysis,numcrica1simu1ationandexperimenta1obscrvation.Butra-diationimpedanceandenergyofthesurfaceradiatorshavenotbeendiscussedyetbynow.… 相似文献
14.
I.IntroductionIn1979,M.R.S.h.o.der[1]pro-posedanewdesignofsounddiffusorwhoseperiodcomprisesNelements(slotsorwells,referedtoaschannelsinfol1owing)ofequalwidths.ThedepthsofchanneIsvaryaccordingtoapseu-dostochasticsequencewithinonepe-riod.Atypicalstructureofq1ladraticresiduediffusor(N=11)isi1IustratedinFig.1.BychoosingthedePtl1ofchannels,thescatteringcharacteristicsofthestructurecanbeoptirnizeds11chastodistributethescattereden(}rgyequalIyoveralloweddirections.In1992,K.Fuiwaraandothers['repo… 相似文献
15.
TheprojectissupportedbyNationalNaturalScienceFoundationofChina.I.IntroductionU1trasonicpropagationandscatteringinthebiologica1softtissuesisabasicprob-lemofbiomedica1u1trasonics,andu1trasonicbackscatteringfromthetissucsproduccs..importantinformationfortissuecharacterizationaswe11asfortissueimagind'.2].Tissuemodellingisfundamentalfortheanalysisofultrasonicbackscattering.Vari-ousmode1shavebeensuggestedwithapartialsuccess.Sofar,therearetwomajortypesofmodc1s,theinhomogeneouscontinuummode1andthed… 相似文献
16.
I.IntroductionMachinenoiseisanenvironmcnta1po11utantanditscontrolremainsamajorunresolvedprob1cm.Inadditiontoair-bornesound,machinesimpartvibrationalenergyintosupportingandconnectedstructuresbybothtrans1ationa1androtationa1motions.Translationa1compo-nentsarerelative1yeasytoestimatesinccnearpureforcescanbegeneratedandmeasured.ThisisnotthecaseforrotationalcomponentSsincemomcntsaremoredifficu1ttogenerateandmeasure.Suchmeasurementswould1eadtoafu11undcrstandingofthis1ittleunderstoodbutoftenimporta… 相似文献
17.
Changes of summating potentials and morphology in theguinea pig cochlea during anoxia 总被引:3,自引:0,他引:3
I.IntroductionThesummatingpotcntia1s(SPs)rcprcscntsaspccificbioe1cctronphenomenonofthecoch1ea.C1inica1lythedominant-SPisnowtakenasasignofrecruitmcnt.However,themechanismofrecruitn1cnt,exccptinMcnicrcdiscase,isnotentireIyunderstood.Thedynamicchangcsinamp1itudcandpolarityofSP,lnrclationtothethrcsho1dshiftofcompoundactionpotential(CAP),SPandcndocochlcapotcntial(EP)inthescalcmcdiawcrcexaminedatonehmewithsing1cmicropipctduringandaftcranoxia.Also,themorpho1ogicchangesinthein-nerhaircc11s(IHC… 相似文献
18.
I.IntroductionUndcrwatersoundrevcrberationhasrccentlybecomeatopicofgreatinterestlI-3l.Sincethcrcverberationincludescombincdeffcctsofsoundpropagahonandscattering,andthesoundpropagationinshallowwaterismuchmorecomplicatedthanthatinthedeepsea,itisnecessarytOstudycarefullybothintheoryandexperimcnt.Fortheshortrangereverberationinshal1owwatcrtheray-basedmodelisavai1ab1e,whilefOr1ongrangethewave-basedmodelmustbeusedbecauscofcomp1icatcdmu1tipaths,refractioneffcctsandfrequencydependence.Thenorma1-mode… 相似文献
19.
SHEN Yaqiang 《声学学报:英文版》1994,(3)
I.IntroductionKa1manfilteringisjustamethodtoestimatestatistica1lythestateoftheobservedsystemfromthecorruptedsigna1s,andthiskindofcstimationisarecurrcneeestimationbasedon1inear,nonbiasandminimumvariance.Moreover,Ka1manfilteringisapplicabletonon-sta-honarysignalsandtime-variantdynamicsystem.Therefore,Kalmanfilteringisveryapplica-bletoenhancingthespeechsigna1sthatarecorruptedbynoise.ThispaperreportStheconcretcmethodofenhanccmentofnoisyspccchanditscxperimentresults.Experimentsindicate:Afterthes… 相似文献
20.
TheprojectissupportedbyAeronauticalScienceFoundation.I.IntroductionThecontro1ofsoundfieldbyintroducingacousticsourcesisatopicofnoisecontrolinwhichanincrcasinginterestisbeingshown.Gcnerallytherearemain1ytwoaspectsinthere-searchesonActiveNoiseContro1(ANC)--theoriesofactivesoundattenuationwhichisthebasementofthetCchnique,anddesignofthecontrolsystem.Recent1y,anewtheorywhichisconsideredtohewc11suitcdtotheanalysisofpracticalproblemshasbeenpresentedbyP.A.Nc1sonetal.[ll.Itshowsthattheminimumpowe… 相似文献